Quote:
Originally Posted by vamfun
I know you want some data, sorry don't have any.
I think this approximation would be true only if the drag torque was of the viscous friction type. Generally, i_free = T_free/kt. If T_free is from bearing coulumb losses then it would not vary with speed. So when you lower the voltage and the motor speed then I would bet i_free would remain fairly constant. There are some components of friction/motor losses that change with speed but I think they are generally small relative to coulumb friction.
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What about armature drag? That aught to be fairly significant.